BACKGROUND<\/p>\n
There are conflicting results on whether the rate of blastocyst development before freezing influences the outcome of frozen-thawed blastocyst transfers.<\/p>\n
METHODS<\/p>\n
We conducted a systematic review and meta-analysis of controlled studies to compare pregnancy outcomes following transfer of thawed blastocysts that were frozen either on Day 5 or Day 6 following fertilization in vitro<\/I>. Searches were conducted on MEDLINE, EMBASE, Cochrane Library and Web of Science. Study selection and data extraction were conducted independently by two reviewers. The Newcastle-Ottawa Quality Assessment Scale was used for quality assessment.<\/p>\n
RESULTS<\/p>\n
We identified 15 controlled studies comprising 2502 frozen-thawed transfers involving blastocysts that were either frozen on Day 5 or Day 6. Meta-analysis of these studies showed significantly higher clinical pregnancy rate [relative risk (RR) = 1.14, 95% confidence interval (CI): 1.03–1.26, P<\/I> = 0.01] and ongoing pregnancy\/live birth rate (RR = 1.15, 95% CI: 1.01–1.30, P<\/I> = 0.03) with Day 5 compared with Day 6 frozen-thawed blastocyst transfers. Sensitivity analysis of those studies where blastocysts frozen on Day 5 or Day 6 were at the same stage of development showed no significant difference in the clinical pregnancy rate (RR = 1.07, 95% CI: 0.87–1.33, P<\/I> = 0.51) and ongoing pregnancy\/live birth rate (RR = 1.08, 95% CI: 0.92–1.27, P<\/I> = 0.36).<\/p>\n
CONCLUSION<\/p>\n
Slower developing blastocysts cryopreserved on Day 6 but at the same stage of development as those developing to the blastocyst stage on Day 5 have similar clinical pregnancy and ongoing pregnancy\/live birth rates following frozen-thawed blastocyst transfers.<\/p>\n","protected":false},"excerpt":{"rendered":"
BACKGROUND There are conflicting results on whether the rate of blastocyst development before freezing influences the outcome of frozen-thawed blastocyst transfers. METHODS We conducted a systematic review and meta-analysis of controlled studies to compare pregnancy outcomes following transfer of thawed … Continue reading